Bone morphometry is applied to the confirmation of the growth and aging of human bones, the diagnosis and confirmation of the rate of progress of bone diseases including osteoporosis and osteomalacia, and the confirmation of the effect of treatment.
Microdensitometry (MD), photon-absorptiometry and radioscopy are generally known bone morphometric methods. Microdensitometry (Kotsu Taisha, Vol. 13, pp. 187-195 (1980); Kotsu Taisha, Vol. 14, pp. 91-104 (1981)) measures the tone of the roentgenogram of a sample bone by a microdensitometer for bone morphometry; photon absorptiometry measures the quantity of gamma rays transmitted through a sample bone by a detector for bone morphometry; and radioscopy measures the quantity of X-rays transmitted through a sample bone by a detector for bone morphometry. A morphometric bone assay method disclosed in U.S. Pat. No. 4,721,112 assays bones on the basis of bone density distribution determined by measuring roentgenographic bone patterns.
Microdensitometry has become increasingly widely used because the method uses readily available roentgenograms which can be easily obtained by an X-ray camera used widely for diagnosing bone fractures. Photon absorptiometry has a drawback in that use of the gamma-ray generator has not become as wide-spread as that of the X-ray camera.
The conventional microdensitometric bone morphometry, however, requires many steps of manual work. When carrying out the conventional microdensitometric bone morphometry, a reference point for bone morphometry is determined in the roentgenographic bone image of a sample bone, an object measuring region, such as a region on a line crossing the middle point of the longitudinal axis of the second metacarpal bone, is selected by a predetermined procedure with reference to the reference point, the selected region is scanned by a microdensitometer, the intensity or quantity, preferably quantity, of light transmitted through the region is measured, and the measured quantity of light transmitted through the region or the measured quantity of light absorbed by the region is recorded as a diagram on a chart. On the other hand, the roentgenogram of an aluminum standard step block, namely, an aluminum step wedge or an aluminum slope, taken together with the roentgenogram of the sample bone is scanned along its longitudinal axis by the microdensitometer, and the measured quantity of light transmitted through or absorbed by the aluminum standard step block is recorded as a diagram on a chart. Then the diagram of the quantity of absorbed light is converted into digital data by a digitizer, the digital data is applied to an electronic computer to convert the quantities of absorbed light at points on the sample bone into corresponding gradations of the aluminum standard step block, and the computer calculates various indices representing the bone-morphology of the region on the basis of a pattern expressed by the gradations of the aluminum standard step block.
Thus, the conventional microdensitometry requires manual work for the selection of the object measuring region in the roentgenogram of the bone, which is troublesome and time-consuming. The light absorption diagram must be scanned by manually operating the digitizer to give the computer the digital data, which is an obstacle to an accurate, quick measurement of the bone. When many sample bones must be measured and many roentgenograms must be analyzed, in particular, the conventional microdensitometry requires much time and labor, which is disadvantageous from an economic viewpoint as well as from that of the rapidity of a measurement.
The tone of the roentgenographic image of the sample bone is greatly dependent on the X-ray condition and developing condition, and the measurement of the roentgenogram is impossible or, even if the roentgenogram can be measured, the measured result includes large errors.
Furthermore, the bone-morphometric examination cannot be performed immediately after the X-ray, because the roentgenogram must be transported from the X-ray place to the roentgenogram examining place far from the X-ray place. Moreover, the installation of both an X-ray apparatus and a bone-morphometric apparatus at the same place requires a morphometric bone assay apparatus in combination with each bone-morphometric apparatus, which increases the cost of the system and labor for the maintenance of the system, and thus is economically disadvantageous.